Btw, is it possible to lock BTS?
The chain has support for creating vesting balance objects, which allows you to lock any asset, and have a variety of unlocking parameters.
Core asset (i.e., BTS) VBO's are created for witness pay and the cashback functionality.
It doesn't really make economic sense to create a VBO, except in a multi-party transaction where one party is either the blockchain, or acting on behalf of the chain. I personally like the idea of a worker proposal to pay people for locking up their BitAssets. For example, if 10k BTS is worth $50, you could create a worker which is funded 10,000 BTS per day, with a business plan of buying $50 BitUSD every day at current market prices, then collecting offers from people based on how many BitUSD they are willing to lock up, and for how long, to get $X of worker's the BitUSD, and then paying out to the top offers in VBO's. You'll always be able to fill it (I'm assuing somebody will always make an offer to be paid $50 to lock up $0.01 for five minutes, and then better offers will come in until the imputed yield gets comparable to any other fixed-income instrument, modulo transaction costs and the market's perception of the probability of certain risk factors unique to BitAssets, like BitUSD black swans or lost/hacked private keys.) It's quite similar to a no-reserve government debt auction, and it seems like a decentralized autonomous fixed-income capability would be attractive to people in these times of zero interest rates. I think this system is a superior replacement for the BTS 0.x yield system because you know what you're getting in advance.
Of course most people I've talked to (including other people here at Cryptonomex) all seem to hate my idea for some reason that they never clearly explain, but blockchain level support for it is there if I ever manage to convince anyone it's a good idea.